Information processing system and method

Abstract

An information processing system and method are disclosed in which information processing is performed in a highly efficient manner using an enabling key block (EKB) on the basis of a tree structure including category subtrees. A key tree is produced so as to include a plurality of subtrees that are grouped in accordance with categories and managed by category entities. An EKB is produced so as to include data produced by selecting a path in the key tree and encrypting an upper-level key in the selected path using a lower-level key in the selected path. The resultant EKB is provided to a device. If a change occurs in state of a category tree capable of processing an EKB identified in the EKB type definition list, a notification of the change in state is sent to an entity that uses the EKB thereby making it possible for an EKB requester to perform processing in accordance with a newest EKB.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to an information processing system, an information processing method, and an information storage medium, and particularly to a data distribution system and method for providing various kinds of data such as content data to an authorized user by means of a process including a cryptographic process. More particularly, the present invention relates to an information processing system, an information processing method, and an information storage medium, in which a key block is produced using a hierarchical-tree key distribution technique depending on a device to which content is to be provided, and the key block is used in encryption of the content and also in transmission of a content key, thereby ensuring that the content, the content key, and other data are securely provided.[0002]It is now very popular to distribute various kinds of software data such as a game program, audio data, and image data (hereinafter, such data...

AI Technical Summary

Benefits of technology

The present invention provides a technique for securely transmitting data only to authorized users without having to perform mutual authentication between a sender and a receiver. This is achieved by producing an enabling key block (EKB) that can be decrypted only by devices that belong to the same category tree as the EKB. The EKB is created by selecting a path in a key tree and encrypting an upper-level key in the selected path using a lower-level key in the selected path. The EKB type definition list identifies which category trees can process the EKB. The key distribution center (KDC) sends a notification of a change in state of a category tree capable of processing an EKB to at least an entity that uses the EKB. The invention allows for efficient production and management of EKBs and ensures that entities can quickly receive notification of changes in the state of a category tree.

Problems solved by technology

The common key is given only to authorized users so that unauthorized users who do not have the common key cannot access the data.

Although an encryption / decryption key can be generated using an output obtained by applying a unidirectional function to, for example, a password determined by a user, it is substantially impossible to determine, from the obtained encryption / decryption key, the password that is original data from which the encryption / decryption key is generated.

This results in inconvenience in renewal.

On the other hand, in the case where the public key encryptography is employed, undesirably complex calculations using a memory with an undesirably high capacity are required.

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